It appears to be an industrial item at the moment. I found several suppliers; mostly from mainland China, and most of them with a MAX forward voltage of around 6.8 V. At every site I visited, they had a signin and a place to "inquire" about prices.

Seems most UV LEDs run at 3.5V @ 100mA. Seeing the max that most PCs offer a USB power is 5V with up to 500mA you'll be limited to using only 4 LEDs. The image below comes from a good LED calc and shows the wiring you'll need for it. That setup will use 400mA. IS you wanted to push things you could use 5 LEDs but then your maxing out the USB port and not all PC/laptops offer a full 500mA to the USB ports. Some max out at 200mA. In which case the lamp wouldn't work at all.